In a large bowl or the bowl of a stand mixer fitted with the dough hook attachment, measure out the sourdough starter, sugar, and warm milk. Mix this into a slurry and then add the flour.

Mix this on low for a minute or until the dough just starts to come together. Let the dough rest for 20-30 minutes.

Next, with the mixer on low add the salt and the butter one tablespoon at a time. Adding each tablespoon of butter as the last is mostly mixed in.

You will want the dough to be at windowpane or close before you stop kneading it.

Windowpane: to check to see if you have reached windowpane take a little bit of the dough and pull it apart until you can see through it without it ripping.

Once the dough has finished kneading place it in a bowl with a lid and let rise on the counter for 12 hours (71 degrees). The dough should have risen some in this time.

NOTE: Remember that enriched sourdough dough takes a long time to rise so this process cannot be rushed!

After the dough has set for around 12 hours take the dough and place on a clean work surface.

Using a rolling pin roll the donuts to about a ¼ inch thickness, maybe slightly thicker. Cut out the donuts using a 3 ½ -inch donut cutter (I use a 3 ½ -inch cookie cutter and a 1 inch for the centers. You can reserve the donut holes and add them to the dough that will be rerolled or place them with the donuts on a parchment paper lined baking sheet.

Continue rolling and cutting out donuts until the dough has been all used. Sometimes I will just roll the last little bit and make it into a round donut.

Once all the donuts are rolled out, cover the donuts loosely with plastic wrap or with a cookie sheet lid like the one linked above. Let rise for 12-14 hours for the second rise.

About 30 minutes before you are ready to fry donuts start your oil (I use canola oil) in your heavy bottom pot. I use enough oil that it’s about 2-3” deep in the pot.  Heat on a medium heat until you reach 350-375 degrees.

NOTE: I find that right around 360 degrees is about perfect for frying. Leaving your thermometer on the side of the pan is a simple way to monitor the temperature to keep the oil within the right range.

While you are waiting for the oil to heat up you will want to make the glaze.

Combine all the ingredients in a small/deep bowl and whisk until well incorporated. Set aside.

Add 2 donuts at a time to the hot oil adjusting the heat as needed to keep the oil hot enough but also not too hot.

Fry the donuts 2 minutes on each side for a total of 4 minutes or until golden brown. Using a slotted metal spatula or spoon, transfer the donuts to a plate that is lined with paper towels to soak up any excess oil. Continue frying the remainder of the sourdough donuts.

Dip the donuts on each side in the glaze while the next batch is frying. You want your donuts to be quite warm but not so hot you can’t hold them when you dip them in glaze. This makes for a beautifully coated donut.

Place the dipped/glazed donut on the cooling rack to cool and the glaze to dry.

Continue with the remaining donuts.

Serve with coffee or a glass of milk.